Working out acceleration from velocity and distance (maths)

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A0W0N
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I know i need to use the formula f=ma but i dont know how to gt acceleration, with these two all i know is acceleration=velocity\time
I'll post the question below.
Appreciate any help
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A0W0N
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papie
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(Original post by A0W0N)
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you are given initial velocity u , distance he takes to stop s, and you know that final velocity v will be 0.
so you can use the equation: v^2 = u^2 + 2as
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papie
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(Original post by A0W0N)
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the you can use f=ma
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A0W0N
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well id hate to ask but I'm stuck on 7ii as well
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papie
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(Original post by A0W0N)
well id hate to ask but I'm stuck on 7ii as well
now that you know the acceleration you can substitute in the same equation the information you are given. initial velocity u is 6, v=0 a=you just found out. solve for s.
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A0W0N
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so does that mean the acceleration will always be the same o for the iii) i could sub 10 in and then find the force required, if thats correct i think i understand these questions now
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papie
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(Original post by A0W0N)
so does that mean the acceleration will always be the same o for the iii) i could sub 10 in and then find the force required, if thats correct i think i understand these questions now
in iii the acceleration is 0 because he moves at constant speed.
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A0W0N
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would thr initial and final velocity be 10 then?
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papie
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you can not use f=ma or any suvat equations here because there is no acceleration
if a=0 then the force he exerts is same as the resistance force both forces cancel out and acceleration is 0. so i guess the force he exerts must be same as the resistance force you found in i.
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A0W0N
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(Original post by papie)
you can not use f=ma or any suvat equations here because there is no acceleration
if a=0 then the force he exerts is same as the resistance force both forces cancel out and acceleration is 0. so i guess the force he exerts must be same as the resistance force you found in i.
but the acceleration in part i was -0.2 so how can it be the same here if acceleration is zero; because he's at a constant speed?
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simon0
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Note also for part iii), use Newton's First Law since the (horizontal) velocity is constant, the sum (horizontal) net force is zero so the force applied must equal the magnitude of the frictional force.
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papie
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(Original post by A0W0N)
but the acceleration in part i was -0.2 so how can it be the same here if acceleration is zero; because he's at a constant speed?
they say it in the question that the Force of Resistance is constant, so no matter the speed the resistance force will stay the same.
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